He educated me that UV does not transits mediums to any concerning levels

Can anybody challenge David's claim here?

Lab science vs my real life experience: I get a tan very fast once I start soaring each season. If I don't use my sunscreen cream (factor 30), after few hours of gliding my face, neck and arms are red. And I also have been explaining to others how plexi transmits UV, unlike glass, except for special quartz glass used in the lamps/bulbs so that people can get the desired tan and pay for it. So what I'm reading posted above turns everything upside down - not so much my scientific knowledge which I have none, but my practical life experience.